A hybrid SDN architecture applies SDN-based control capabilities onto the existing transport infrastructure utilizing a distributed control plane instead of a centralized control plane as is utilized in a standard SDN architecture. One example of a hybrid SDN architecture, referred to as horizontal split, is when the service related functions are provisioned by the central SDN controller while the simpler transport functions (e.g., maintaining connectivity between the nodes of the network domain) are implemented using legacy, distributed methods.
FIG. 1 is a diagram of one embodiment of a basic embodiment of a hybrid SDN implementation. The hybrid SDN includes a service controller that provides a set of services to each of the hybrid SDN node in the hybrid SDN architecture. The hybrid SDN nodes utilize distributed transport protocols for inter-communication and routing between the hybrid SDN nodes using interior gateway protocol (IGP) or similar distributed protocol. The service controller communicates with each of the hybrid SDN nodes using a flow control protocol.
The flow control protocol, such as OpenFlow or similar flow control protocol, specifies a protocol for configuring and managing the FIB of a data plane node. A flow control compliant data plan implements a logical view of its FIB, referred to as the logical switch. All configuration actions are performed on this logical view, i.e., on the logical switch. The node then transforms the configuration information elements of the logical switch into actual FIB entries. The configuration information elements represent the forwarding information of the logical switch. Some specific implementations specify a protocol for configuring a managing logical switch instances, such as OpenFlow Configuration (OF-CONFIG). The different logical switch instances of the same node can be driven and configured by different controllers via this protocol.
However, the concepts related to hybrid SDN implementation that have been proposed have significant limitations in their implementations. In particular, the coherence of their proposed implementation is not assured or well defined. Thus, significant difficulties remain to implementing a hybrid SDN architecture.